Fall came early in Piney Orchard, and the community swimming pool was still full of water when the first frost occurred. The outside temperature hovered at 30° F. Maintenance quickly turned off the heat so that energy would not be wasted heating a pool that nobody would be swimming in for at least six months. As Tess walked by the pool each day on her way to school, she would peer through the fence at the slowly cooling pool. She could just make out the thermometer across the deck that displays the water’s temperature. On the first day, she noted that the water temperature was 68° F. Four days later, the temperature reading was 58° F. If the outside temperature remains at 30° F, and the pool is allowed to continue to cool, how long before it freezes (32 oF)? Write an equation that models this situation. Heating and cooling problems are typical application problems that use exponential equations of the form .